CD4 to CD8 ratio calculator
CD4 helper T cells divided by CD8 cytotoxic T cells. It shows how those two groups of T cells balance. Type your results in the units on your report and it works out CD4/CD8 ratio as you type, in your browser.
AI-verified against cited sources. Awaiting expert reviewLast reviewed 2026-10-03Immune System
Type your results above, or fill in the example, to see CD4/CD8 ratio.
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Educational information, not medical advice. Blood Test Tracker doesn’t diagnose or treat, and it doesn’t replace your clinician. Talk with your clinician before changing medications, supplements or care.
How it’s worked out
The formula
CD4+ T cells (cells/µL) ÷ CD8+ T cells (cells/µL). The two percents from the same sample give the same ratio, because the unit cancels.
A worked example
Example numbers, not anyone’s real results, run through the same code as the calculator above.
| CD4 count | 900 cells/µL |
|---|---|
| CD8 count | 500 cells/µL |
| CD4/CD8 ratio | 1.80 ratio |
For an adult, this result is in the usual range.
What CD4/CD8 ratio tells you
This number is calculated from your CD4 and CD8 T-cell results. CD4 cells help direct the immune response, and CD8 cells destroy infected or abnormal cells. In many healthy adults there are more CD4 cells than CD8 cells, so the ratio is above 1. A ratio below 1 is called inverted. Using the two absolute counts or the two percents from the same sample gives the same ratio.
The ratio is a quick way to see the balance between helper and cytotoxic T cells. In people with HIV it is often low, and it can stay low even when CD4 counts recover. Outside HIV, a low ratio has been linked in research to an aging immune system and to long-term infection with cytomegalovirus (CMV). A single ratio cannot tell you why it is high or low, and some healthy people have an inverted ratio.
Read the full page on CD4/CD8 ratio, with what a high or low result can mean.
Usual ranges
The ranges the result above is placed on. Your own lab’s printed range comes first if it gives one.
- 16–640.8–3.9 ratio
Sources: ARUP Laboratories, PLoS Pathogens, Immunobiology (University of Miami)
- 65+0.8–6.17 ratio
Source: ARUP Laboratories
- 2–40.9–2.9 ratio
Source: ARUP Laboratories
- 5–90.9–2.6 ratio
Source: ARUP Laboratories
- 10–150.9–3.4 ratio
Source: ARUP Laboratories
Sources
The equation
- Lymphocyte Subset Panel 4 - T-Cell Subsets Percent and Absolute, Whole Blood (test 0095950), ARUP Laboratories
- Imbalance in the game of T cells: What can the CD4/CD8 T-cell ratio tell us about HIV and health?, PLoS Pathogens (2017)
1 more sources for the ranges and the explanation
- Reference ranges of lymphocyte subsets in healthy adults and adolescents with special mention of T cell maturation subsets in adults of South Florida, Immunobiology (University of Miami) (2014)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. The calculator is version 1.0.0 of our code for this equation, tested against published examples. How we build and check these pages.